Tool with moment indication

ABSTRACT

A tool is provided for the exertion of a turning moment, including an indication as to whether the turning moment exceeds a set value, in which a form piece (4) with parallel rectangular surfaces turns when the turning moment attains the set value and pushes a press bolt (3) situated in the shaft (2) and a indication sleeve (6) situated outside the shaft, said indication sleeve being connected with the press bolt, towards the grip (11) so that a previously hidden part of the indication sleeve (6) with a contrasting color becomes visible.

BACKGROUND OF THE INVENTION

Tools for the rotation of screws, nuts and other threaded objects areoften provided with a moment measuring or moment indicating appliance inorder to guarantee that the tightening moment be within a prescribedrange, since too low a moment does not give a tight joint and too high amoment damages the threaded object. Also for other tools intended forexerting a turning moment, there is a need for measuring or indicatingthe magnitude of the turning moment, e.g. when controlling the turningmoment in springs, axles or bolts.

Basically, there exist two different types of tools. When using a momentmeasuring tool, the moment is determined as a deformation in some partof the tool, for instance in an elastic joint or in the shaft as suchand the deformation can be read by an index on a scale or by digitalelectronics. However, the reading requires that the tool be moved slowlyand that the scale be clearly visible, wherefore this type is unsuitablefor routine installation work. Moment indicating tools merely indicatewhether the moment is above or underneath an initially determined value,and is faster to work with when many screws are to be tightened with thesame moment.

When using moment indicating tools, the difficulty resides in achievingan indication which is easily readable also under difficult conditionswith noise and bad visibility. The invention foresees a tool with whichthe indication is effected in several simultaneous ways.

BRIEF DESCRIPTION OF THE DRAWING

One embodiment of the present invention is a ratchet handle which ispartially shown in a cross-section in FIGS. 1 and 2, in which:

FIG. 1 shows the position of the separate parts when the moment is lessthan the set value, and

FIG. 2 shows the position of the different parts when the moment exceedsthe set value.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A ratchet handle according to the present invention includes a grip 11,a hollow shaft 2 and a head 12 with a protruding axle to which differentsleeves can be coupled, depending on the size of the threaded objects.Preferably, the head 12 includes a stepping mechanism. The head 12 isfixedly connected to an arm 1 which protrudes into the shaft 2, the headbeing restricted in its angular movement in relation with the shaft tubeby a joint 10. Inside the shaft 2 there is a slidable press bolt 3 whichcan be urged against the head 12 by a helical spring 7. By turning thegrip 11, the helical spring 7 can be compressed to different extents sothat the force in the helical spring is adjustable and can be read on ascale on the grip 11.

Between the arm 1 and the press bolt 3 a form piece 4 is inserted withparallel rectangular surfaces. The form piece 4 abuts plane surfaces onthe arm 1 and on the press bolt 3, which surfaces are delimited byprotruding edges.

The press bolt 3 is connected to a slidable indication sleeve 6 on theoutside of the shaft 2 via one or several pins 9 which penetrateelongated slots in the shaft tube, the indication sleeve preferablybeing made with a contrasting colour over the other parts. Outside theindication sleeve 6 there is a covering sleeve 5 which is fixedlyconnected with the shaft 2 by one or several set screws 8.

When the moment on the axle of the head 12 gets less than a value whichis dependent upon the set force in the helical spring 7, then theparallel surfaces of the form piece 4 come into contact with the planesurfaces of the arm 1 and the press bolt 3, the arm 1 being forced to acentral positioning within the shaft 2, whereby the protruding edges ofthe plane surfaces render this central position well defined andreproducible. Thereby, the indication sleeve 6 is hidden within thecover sleeve 5.

When the moment on the axle of the head 12 exceeds the value which isdependent upon the set force in the helical spring 7, then the formpiece 4 turns so that only its edges but not its parallel surfaces comeinto contact with the press bolt 3 and the arm 1. Then the press bolt 3and the indication sleeve 6 move towards the grip 11. This can beobserved in four different ways. The first indication is that as soon asthe form piece 4 starts turning, then the movability of the shaft 2 andthe grip 11 increases around the joint 10, which is sensed by the user.The second indication is that the arm 1 abuts against the inside of theshaft 2 with a hearable sound. The third and the fourth indication isthat when the indication sleeve 6 moves towards the grip 11, itprotrudes out of the cover sleeve 5, which is visible from manydifferent directions by the fact that the indication sleeve has acontrasting colour, and can also be felt with a finger.

In comparison with other constructions for similar uses, the inventionmakes it possible to observe the attainment of the desired moment inseveral ways, including cases where the tool is difficult or impossibleto observe. The rectangular shape of the parallel sides of form piece 4is less submitted to wear than other known constructions, cf. forinstance U.S. Pat. No. 5,123,289, because of the fact that the edges areunloaded when the set moment has not been exceeded, and also gives abetter defined and play-free central positioning of the arm 1.

Ratchet handles for the rotation of threaded objects represent only oneembodiment of tools according to the invention, which can also be formedfor the rotation of threaded objects without any stepping function inthe head 12, or for the control of torsional moments in springs, axlesand bolts. The spring 7 can be a helical spring and also, e.g., one orseveral cup springs.

Although only preferred embodiments are specifically illustrated anddescribed herein, it will be appreciated that many modifications andvariations of the present invention are possible in light of the aboveteachings and within the purview of the appended claims withoutdeparting from the intended scope of the invention.

We claim:
 1. A tool for the exertion of a turning moment with anindicator for showing whether the turning moment exceeds a set value,comprising:a hollow shaft, a grip, a head at which the turning moment isexerted, a joint between the head and the shaft, an arm joined with thehead and protruding into the shaft, said arm having a substantiallyplanar surface, and a spring within the shaft, a press bolt between thearm and the spring, said press bolt is slidable in the shaft and has asubstantially planar surface, and a form piece with parallel surfaceswhich abut the planar surfaces of the press bolt and of the arm when theturning moment is less than a set value, an indication sleeve on theoutside of the shaft is connected to the press bolt, and the indicationsleeve is hidden when the turning moment is less than the set value,wherein when the turning moment attains or exceeds the set value theform piece turns and contacts the planar surfaces only with its edges,displacing the press bolt and the indication sleeve along the shafttowards the grip, thus exposing a part of the indication sleeve.
 2. Toolaccording to claim 1, wherein the part of the indication sleeve has acontrasting colour.
 3. Tool according to claim 1, wherein the planarsurfaces of the press bolt and the arm have protruding edges.
 4. Toolaccording to claim 1 wherein the parallel surfaces of the form piece arerectangular.
 5. Tool according to claim 1 wherein the head is providedwith a protruding axle in order to couple sleeves for the rotation ofthreaded objects.
 6. Tool according to claim 2, wherein the planarsurfaces of the press bolt and the arm have protruding edges.
 7. Toolaccording to claim 2, wherein the parallel surfaces of the form pieceare rectangular.
 8. Tool according to claim 2, wherein the head isprovided with a protruding axle in order to couple sleeves for therotation of threaded objects.